workshop theory and practice.pptx

8/10/2019 workshop theory and practice.pptx

1/35


2/35

CUTTING TOOLS

ANDFLUIDS


3/35

METAL CUTTING


4/35

CUTTING TOOLS

THE SIMILE OF AN AXE CUTTING WOOD WAS

OFTEN USED INCORRECTLY TO ILLUSTRATETHE ACTION OF A CUTTING TOOL.


5/35

METAL-CUTTING TERMINOLOGY


6/35

A NUMBER OF TERMS RESULTED

FROM THE RESEARCH CONDUCTEDON THE METAL CUTTIN, AND IT

MAY BE WISE TO CLEAR DEFINE

THIS TERMS


7/35

A BUILT-UP EDGEIS A LAYER OF

COMPRESSED METAL FROM THEMATERIAL BEING CUT WHICH

ADHERES TO AND PILES UP ON THE

CUTTING TOOL EDGE DURING AMACHINIG OPERATION.


8/35

THE CHIP-TOOL INTERFERENCE IS

THE PORTION OF THE FACE OF THECUTTING TOOL UPON WHICH THE

CHIP SLIDES AS IT IS CUT FROM

THE METAL.


9/35

PLASTIC DEFORMATION IS THE

DEFORMATION OF THE WORKMATERIALS OCCURING IN THE

SHEAR ZONE DURING A CUTTING

ACTION.


10/35

PLASTIC FLOW IS THE FLOW OF

METAL OCCURING ON THE SHEARPLANE WHICH EXTENDS FROM THE

CUTTING TOOL EDGE.


11/35

A RUPTURE IS THE TEAR THAT OCCURS

WHEN BRITTLE MATERIAL, SUCH AS CAST

IRON, ARE CUT AND THE CHIP BREAKS

AWAY THE SURFACE. THIS GENERALLY

OCCURS WHEN DISCONTINUOUS OR

SEGMETED CHIPS ARE PRODUCED.


12/35

THE SHEAR ANGLE OR PLANEIS

THE ANGLE OF THE AREA OF THEMATERIAL


13/35

Is the area where plastic deformation of the metal occurs. It isalong a plane from the cutting edge of the tool to its originalwork surface.

Shear Zone


14/35

MACHINING OPERATION PERFORMED

ON LATHES, SHAPERS, MILLINGMACHINE, OR SIMILAR MACHINE

TOOLS PRODUCED CHIPS WHICH

FALL INTO THREE BASIC TYPES.


15/35

Type 1: discontinuous

(segmented) chips-> are produced when brittle

metals, such as cast iron

and hard bronze, or someductile metals are cut under

poor cutting conditions.


16/35

Type 2: continuous chip

is a continuous ribbonproduced when the flow of

metal next to the tool face

is not greatly retarded by abuilt-up edge at the chip

tool interface.


17/35

Type 3: continuous chip with

a built-up edge-> Low-carbon machine steel,

when cut with a high sped

steel cutting tool withoutthe use of cutting fluids,

generally produces a

continuous-type chip with a

built-up edge.


18/35

DESCRIBES THE EASE ORDIFFICULTY WITH WHICH A METAL

CAN BE MACHINED. SUCH

FACTORS AS CUTTING TOOL LIFE,

SURFACE FINISH PRODUCED, ANDPOWER REQUIRED MUST BE

CONSIDER.

MACHINABILITY OF METALS


19/35

THE MACHINABILITY OF A METAL IS AFFECTED BYITS MICROSTRUCTURE AND WILL VARY IF THEMETAL HAS BEEN ANNEALED. CERTAINCHEMECAL NAD PHYSICAL MODIFICATION OFSTEEL WILL IMPROVE THERE MACHINABILIY .FREE-MACHINING STEELS HAVE GENERELLYBEEN MODIFIED IN THE FOLLOWING MANNER BY:

*THE ADDITION OF SULFUR

*THE ADDITION OF LEAD

*THE ADDITION OF SODIUM SULFITE

*COLD WORKING WHICH MODIFIES THEDUCTILITY

GAIN STRUCTURE


20/35

BY MAKING THESE(FREE-MACHINIG) MODIFICATIONS TO THE STEEL, THREEMAIN MACHINING CHARACTERISTICSBECOME EVIDENT:

*TOOL LIFE IS INCREASED

*A BETTER SURFACEFINISH IS PRODUCED

*LOWER POWER CONSUMPTIONIS REQUIRED FOR MACHINING


21/35

THE MICROSTRUCTURE OF LOW-CARBON STEEL MAY HAVE LARGE

AREAS OF FERRITE ANTERPPERSED WITH SMALL AREAS OF

PEARLITE. FERIEIS SOFT WITH HIGH DUCTILITY AND LOW

STRENGTH, WHILE PEARLITE, A COMBINATION OF FERRITE AND

IRON CARBIDE, HAS LOW DUCTILITY AND HIGH STRENGHT.

LOW-CARBON(MACHINE) STEEL


22/35

A GREATER AMOUNT OF PEARLITE IS PRESENT IN HIGH CARBONSTEEL BECAUSE OF THE HIGHER AMOUNT OF CARBON CONTENT.

THE GREATER AMOUNT OF PEARLITE (LOW DUCTILITY AND HIGHSTRENGH) PRESENT IN THE STEEL, THE MORE DIFFICULT IT BECOMESTO MACHINE THE STEEL EFFICIENTLY.

MICROSTRUCTURES DRILL BITS HEXAGON DIE

HIGH-CARBON(TOOL) STEEL


23/35

WHICH ARE ACOMBINATION OF TWO METALS ARE GENERALLYLITTLE MORE DIFFICULT TO MACHINE THEN LOW OR HIGH-CARBONSTEELL. INORDER TO IMPROVE THEIR MACHINING QUALITES,COMBINATIONS OF SULFUR AND LEAD OR SULFUR ANDMANGANESE IN PROPER PROPORTION ARE SOMETIMES ADDEDALLOY STEEL.

ALLOY STEEL


24/35

CONSISTINGGENERALLY OF FERRITE, IRON CARBIDE, AND FREECARBON, FORM AN IMPORTANT GROUP OF MATERIALS USED BYINDUSTRY. THE MICROSTRUCTURE OF CAST IRON CAN BECONTROLLED BY THE ADDITION OF ALLOYS, THE METHOD OFCASTIG , THE RATE OF COOLING AND BY HEATING

WHITE CAST IRON

GREY CAST IRON

CAST IRON


25/35


26/35

*REDUCTION OF TOOL COST. Cutting fluids reduced toolware

*INCREASED SPEED OF PRODUCTION. Because cuttingoils help reduce heat and friction, higher cutting speed canbe used in the operation

*REDUCTION OF POWER COST. Since friction is reduced by

a cutting fluid, less power is required for machiningoperation and a corresponding saving in power cost ispossible.

*BETTER SURFACE FINISH. Since cutting fluids reducefriction and prolong the keen edge of cutting tools, bettersurface finishes and dimensional accuracy can be obtained.

Purposes and Advantages

CHARACTERISTICS OF A GOOD CUTTING


27/35

GOOD COOLING CAPACITY

To reduce the cutting temperature, increase tool life and production, and improve

dimensional accuracy GOOD LUBRICATING QUALITIES

to prevent metal from adhering to the cutting edge, forming a built-up edge, resultingin a poor surface finish.

RUST RESISTANCE

which should eliminate stain, rust or corrosion to the work piece or machine.

Stability

both on storage or in use

RESISTANCE TO RANCIDITY

NONTOXICITY

so it will not cause skin irritation to the operator.

TRANSPARENCYso that the operator can clearly see the work during machining

NONFLAMMABLE

so it will not burn easily and preferably be noncombustible, as well as notsmoke excessively, form gummy deposit which may cause machine slides to becomesticky

CHARACTERISTICS OF A GOOD CUTTING

FLUIDS


28/35

Cutting oils are classified under two types: active and inactivecutting oils.

These terms relate to the oils chemical activity or ability to

react with the metal surface at elevated temperature to protectit and improve the cutting action

CUTTING OILS


29/35

Which may be dark or transparent, fall into 3 general categories SULFURIZED MINERAL OILSThey are useful for cutting of

low-carbon steel and tough, ductile metals.

SULFOCHLORONATED MINERAL OILThese oil preventexcessive built-up edges from forming and prolong the life ofthe cutting tool. Also effective on low-carbon and chrome nickelalloy steel

SULFOCHLORINATED FATTY OIL BLEND

Contains moresulfur than the other types and are effective cutting fluids forheavy-duty machining.

Active Cutting Oils


30/35

Where the sulfur is so firmly attached to the oil that the every little isreleased to react with the work surface during the cutting action, fallinto four general categories.

STRAIGHT MINERAL OILSThey used for the nonferrous metalssuch as aluminum and brass.

FATTY OILSThey are generally used for severe cutting operationon tough, nonferrous metals where a sulfurized oil might causediscoloration.

FATTY AND MENIRAL OIL BLENDAre combinations of fatty andmineral oil, resulting in better wetting and penetrating qualities than

straight mineral oils. SULFURIZED FATTY-MINERALS OIL BLENDSthey often used on

machine when ferrous and nonferrous metals are machined at thesame time

Inactive Cutting Tools


31/35

AN EFFECTIVE CUTTING FLUIDSHUOLD POSSES HIGH HEATCONDUCTIVITY, AND NIETHER MINERAL NOR FATTY OIL ARE VERYEFFECTIVE AS COOLANTS. WATER IS THE BEST COOLING KNOWN;HOWEVER USED CUTTING FLUID, WATER ALONE WOULD CAUSE RUSTAND HAVE LITTLE LUBRICATING VALUE. BY ADDING A CERTAINPERCENTAGE OF SOLUBLE OIL TO WATER, IT IS POSSIBLE TO ADDRUST-RESISTANCE AND LUBRICATION QUALITIES TO THE EXCELLENTCOOLING CAPABILITIES OF WATER.

EMULSIFIABLE OILS


32/35

Sometimes called as synthetic fluids, have been widely accepted since theywere first introduced for machining purposes.

As a result of the chemical agents which are added to the cooling qualities ofwater, synthetic fluids provide the following advantages:

Good rust control

Resistance for long period of time to becoming rancid

Excellent cooling quantities

longer durability than cutting or soluble oils

They are nonflammable

They are nontoxic

Easy separation from the work and chips, which makes them clean towork with.

No clogging of the machine cooling system due to detergent action ofthe fluid

CHEMICAL CUTTING FLUIDS


33/35

Cutting tool life and the machiningoperation are greatly influenced by

the way that the cutting fluid is

applied.

Application of cutting fluids


34/35


35/35

In slab milling, cutting fluid should be directed toboth sides of the cutter by fan-shaped nozzlesapproximately three- forths the width of the cutter

Milling

Documents

workshop theory and practice.pptx